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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

Résilience systémique d’un territoire composé d’activités essentielles suite à une perturbation majeure – Approches systémique et spatiale / Systemic resilience of territory composed of essential activities – Spatial and systemic approaches

Rey, Benjamin 02 April 2015 (has links)
De trop nombreux évènements survenus la décennie passée illustrent la gravité et l’étendue des impacts auxquels les territoires peuvent être confrontés. L'atteinte aux infrastructures critiques peut induire de très nombreux dysfonctionnements en cascade pouvant plonger ce territoire et sa société dans une crise de grande ampleur. Les interdépendances entre ces activités essentielles et celles avec la population accentuent leur fragilité. Afin d'évaluer les impacts directs et indirects d'une perturbation majeure, la méthodologie développée étudie la problématique sous un angle multisectoriel répondant ainsi à une prise en compte de la complexité des territoires. Dans un premier temps, le territoire via ses activités essentielles et sa population est modélisé en s'appuyant sur les liens d'interdépendance existants. Sur la base d'un évènement initial donné, la méthode identifie les scénarios de propagation possibles et leurs conséquences sur les "usagers" concernés par la délivrance des services touchés. Cette simulation permet ainsi d'apprécier la résilience systémique des enjeux du territoire. Basé sur une approche systémique et spatiale, ce travail a pour objectif de fournir une aide à la décision à la planification des mesures de continuité et de rétablissement d'activité ou à la mise en place de mesures de traitement des risques. / Too many dramatic events occurred over the last ten years have demonstrated the severity and extent of impacts that territories may be confronted with. Damages to critical infrastructures may have a variety of downfall disturbing effects, which can lead territories and society into a huge crisis. Interdependency between these essential activities on the one hand, and between these activities and the population on the other hand, increases their vulnerability. This thesis presents a methodology to better assess direct and indirect impacts of a major disturbance. The issue is addressed from a multi-activity perspective, to take into account territories complexity.In the first stage, a territory is modeled using existing interdependency links between essential activities and the population. The methodology then identifies, based on a defined initial event, possible propagation scenarios and their consequences on services “users”. Finally, this simulation gives an assessment of the territory stakes resilience. This works provides a decision-making tool for the development of activity continuity plans, or risk assessment and mitigation policies.
2

Spatial aspects of bumble bee (Bombus spp. Apidae) foraging in farm landscapes

Schaffer, M. J. January 1997 (has links)
Bumble bees (Bombus spp.: Apidae) are valuable pollinators of many crop and wildflower species. However, in some situations their potential is limited. Evaluation of, and management to improve bumble bee efficacy should include spatial information which is currently limited. Distance and direction determine the success of gene flow via pollen cross-over within and between plant populations at several scales. Studies of movement by bumble bees at large scales in semi-natural and intensively managed habitats are scarce. Few studies of bumble bee dispersal from the nest exist, particularly in relation to crops. At a small scale, directional rather than random movement between flowers has benefits for pollen flow. Results to date of directionality studies at small scales and their interpretation are inconsistent. The purpose of this thesis was to assess distances and directions moved by foraging bumble bees at a range of scales in two contrasting farm habitats in order to predict their pollination potential. A novel method was developed to mark automatically all the occupants of nests of bumble bees B. terrestris (L.) placed around a Lucerne seed crop Medicago sativa L. in New Zealand. Reobservation data from eight nests showed that of bumble bees which foraged within the crop, 81 % travelled ≤ 50 m and 56% ≤ 20 m from their nest. Results should be interpreted with extreme caution because fewer than 1 % of bumble bees marked at nests were reobserved in the crop. Because it was not established where the other 99% of the bumble bees went, foraging areas for nests could not be calculated as anticipated. Theories to explain the non-specificity of bumble bees to the crop include; resource depletion near nests, competition with honey bees in the crop, or an evolved strategy to disperse in order to minimise nest predation. Lucerne flowers contained a significantly lower concentration of sugar in nectar, and significantly fewer pollen grains than did those of purple loosestrife Lythrum salicaria L., a species on which bumble bees appeared to forage in preference Lucerne. The higher rewards offered by L. salicaria may have diverted bumble bees from the less-rewarding Lucerne crop. In a Norwegian meadow system, all foraging bouts by bumble bees B. lucorum (L.) within a patch of wood cranesbill flowers Geranium sylvaticum L. were random with respect to direction. This result is not consistent with predictions, based on optimal foraging theory, that movement should be directional to enable optimal pollen flow, and to avoid revisitation of just-emptied flowers by the pollinator. A medium-scale study of several bumble bee species moving between patches of northern wolfsbane Aconitum septentrionale Koelle in Norway revealed considerable loyalty by bumble bees to patches in which they were marked. In a different landscape-scale study (over 5 ha), several bumble bees exhibited a high degree of loyalty to areas in which they were marked (87% were reobserved ≤ 50 m from marking points). These restricted movement patterns are discussed in terms of potential pollen flow. Of 260 bumble bees marked, only five were recorded crossing between meadows, which could be a result of innate loyalty to small forage areas, an artefact of the sampling technique used, or forest boundaries acting as physical impediments to movement. In the future, spatial data of the type collected in this thesis will aid in the management of bumble bee populations to achieve both commercial and conservation goals. Spatial data can be applied to predict the optimal placement of artificially-reared nests, predict suitable isolation distances for pure seed crops, and aid in the positioning of supplementary forage sources and nest-site refuges.
3

Uma abordagem híbrida baseada em Projeções sobre Conjuntos Convexos para Super-Resolução espacial e espectral / A hybrid approach based on projections onto convex sets for spatial and spectral super-resolution

Cunha, Bruno Aguilar 10 November 2016 (has links)
Submitted by Milena Rubi ( ri.bso@ufscar.br) on 2017-10-17T16:07:35Z No. of bitstreams: 1 CUNHA_Bruno_2017.pdf: 1281922 bytes, checksum: 605ecd45f46a3b67332ed6bd13043af5 (MD5) / Approved for entry into archive by Milena Rubi ( ri.bso@ufscar.br) on 2017-10-17T16:07:44Z (GMT) No. of bitstreams: 1 CUNHA_Bruno_2017.pdf: 1281922 bytes, checksum: 605ecd45f46a3b67332ed6bd13043af5 (MD5) / Approved for entry into archive by Milena Rubi ( ri.bso@ufscar.br) on 2017-10-17T16:07:53Z (GMT) No. of bitstreams: 1 CUNHA_Bruno_2017.pdf: 1281922 bytes, checksum: 605ecd45f46a3b67332ed6bd13043af5 (MD5) / Made available in DSpace on 2017-10-17T16:08:04Z (GMT). No. of bitstreams: 1 CUNHA_Bruno_2017.pdf: 1281922 bytes, checksum: 605ecd45f46a3b67332ed6bd13043af5 (MD5) Previous issue date: 2016-11-10 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / This work proposes both a study and a development of an algorithm for super-resolution of digital images using projections onto convex sets. The method is based on a classic algorithm for spatial super-resolution which considering the subpixel information present in a set of lower resolution images, generate an image of higher resolution and better visual quality. We propose the incorporation of a new restriction based on the Richardson-Lucy algorithm in order to restore and recover part of the spatial frequencies lost during the degradation and decimation process of the high resolution images. In this way the algorithm provides a hybrid approach based on projections onto convex sets which is capable of promoting both the spatial and spectral image super-resolution. The proposed approach was compared with the original algorithm from Sezan and Tekalp and later with a method based on a robust framework that is considered nowadays one of the most effective methods for super-resolution. The results, considering both the visual and the mean square error analysis, demonstrate that the proposed method has great potential promoting increased visual quality over the images studied. / Este trabalho visa o estudo e o desenvolvimento de um algoritmo para super-resolução de imagens digitais baseado na teoria de projeções sobre conjuntos convexos. O método é baseado em um algoritmo clássico de projeções sobre restrições convexas para super- resolução espacial onde se busca, considerando as informações subpixel presentes em um conjunto de imagens de menor resolução, gerar uma imagem de maior resolução e com melhor qualidade visual. Propomos a incorporação de uma nova restrição baseada no algoritmo de Richardson-Lucy para restaurar e recuperar parte das frequências espaciais perdidas durante o processo de degradação e decimação das imagens de alta resolução. Nesse sentido o algoritmo provê uma abordagem híbrida baseada em projeções sobre conjuntos convexos que é capaz de promover simultaneamente a super-resolução espacial e a espectral. A abordagem proposta foi comparada com o algoritmo original de Sezan e Tekalp e posteriormente com um método baseado em um framework de super-resolução robusta, considerado um dos métodos mais eficazes na atualidade. Os resultados obtidos, considerando as análises visuais e também através do erro médio quadrático, demonstram que o método proposto possui grande potencialidade promovendo o aumento da qualidade visual das imagens estudadas.
4

Who is Addressing the Deficiency in the Literature on the Prosperous Development of Outer Space? : A comparative approach to the interconnected issue of the absence of a space power theory, and the controversy surrounding the definition and delimitation of outer space.

Reed, Linea January 2023 (has links)
As outer space becomes more commercialized, humans have invested more time and efforts into the use and exploration of the outer space domain. Captured by the display of opportunities, space is becoming increasingly overcrowded. Currently, the only framework fully embracing the exploration and use of outer space is the Outer Space Treaty (OST), put forward by the United Nations in 1967. While the OST is detailing how space faring nations ought to peacefully use outer space as a joint arena for technological development, the discourse on outer space governance still experience some serious definitional limitations. This paper examines two interconnected deficiencies in the literature on outer space; first, the insufficient research and development of a space power theory and; second, the absence of, and the challenges in constructing and all- encompassing definition and/or delimitation of outer space. To support the discussion and to reach some definitive conclusions of the current status of these issues, a selection of historical theories and contemporary cases have been applied to enrich the debate. By identifying gaps in the literature, this paper strives to highlight some of the controversies in the outer space discourse.

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